(1) Field of the Invention
This invention generally relates to molding of plastics and specifically to a method of producing an essentially self-supporting stratiform article, typically a trim panel of the type used in the interior of automotive vehicles such as vertical wall panels including door panels.
(2) Description of the Prior Art
Generally, trim panels for automobiles are composed of a substrate or base layer for mechanical strength and of an outer cover for visual appearance, feel, and/or comfort. Also, the outer cover frequently comprises more than one area with a specific or distinct color, texture, or resilience; for example, one or more vinyl-covered area(s) for resistance against soil and abrasion are combined with one or more, e.g. two to four areas covered with a textile such as carpeting, cloth or velvet, a foamed layer, man-made or natural leather for pleasing appearance, comfort or soil resistance.
Safe and easy placement of segments of cover stock cut in accordance with the surface area(s) that is (are) to be provided with the particular cover layer, and--most importantly--in close register with one or more selected area(s), presents several problems some of which may need mutually exclusive solutions so as to require some compromise in the balance of properties.
Most of the problems connected therewith tend to be aggravated by the fact that typical trim panels are "profiled", i.e. not essentially planar but shaped "three-dimensionally" to some extent so as to have a "depth" dimension in addition to having width and length. For example, protruding arm rests previously made as separate parts for subsequent mounting on a trim panel should be molded integrally with the panel to simplify production, and such arm rests, typically, require a specific surface structure, be it for comfort of use or for visual appearance. Additional problems are encountered when environmental requirements must be met, e.g. regarding disposal or recycling, or when some desired properties of a material defy meeting another requirement, e.g. the desirable toughness of polypropylene contrasted with its adhesive-repellant surface properties. Further, various aspects of the problems involved, such as structural integrity, ease of manufacture and off-set avoidance tend to increase, sometimes geometrically, with the number of the differing cover segments, e.g. more than two and up to eight or even ten.
The art is replete with teachings of methods for making trim panels and the disclosure in U.S. Pat. Nos. 4,781,956, 4,779,390, 4,810,452, 4,830,929 and 4,873,045 is mentioned by way of example representing what applicant feels to be the most pertinent art herein. Yet, the multiplicity of methods proposed previously might be an indication of the fact that no generally satisfactory method has been found up to now, notably when mass production technology is concerned.